The present invention relates to a filter apparatus for producing aromatic extracts of coffee or tea. More particularly, the invention relates to a filter apparatus of the type which includes a filter vessel and a filter paper insert adapted to the filter vessel, with the interior of the filter vessel and thus of the filter paper insert having a pyramid-like shape when in use.
A filter apparatus of this type is disclosed in German Patent 2,221,831.
In addition to this prior art filter apparatus, there exist other basic structures for producing aromatic extracts from coffee or tea.
For example, conical filters which are used primarily in the home are known. Due to their configuration, the capacity of such conical filters is limited, so that using such conical filters commercially, where the required capacity is large, is impractical for reasons of space.
Additionally, there exist the so-called basket filters which are employed in the home as well as commercially. Although the filter paper inserts for such basket filters can be manufactured relatively easily, they have the drawback that they are not very stable in form and must be stacked on top of one another, which makes the use of such filter paper inserts awkward. Another drawback of this type of structure is that the water distributors employed must be designed with broad faces, since otherwise it would not be possible to fully utilize the aroma carrier (e.g., coffee or tea). The aroma carrier is used inefficiently in any case if a small amount is brewed with the aid of a basket filter, since only a relatively small quantity of the aroma carrier is distributed over the large area available.
Experience has shown that such basket filters are also very sensitive to differences in the quality of the water, particularly with respect to the effective filtration period. The shower head-like water distributors required ar susceptible to calcium deposits and soiling.
So-called flat filters are also known. However, essentially the same drawbacks apply as for the so-called basket filters.
Moreover, filter apparatuses of the generic type disclosed in German Patent 2,221,831 have a number of advantages.
For example, the manufacture of filter paper inserts for such filter apparatuses is rather simple, as indicated in German Patent 2,221,831. The capacity of such filter apparatuses is also very large with a sufficiently large effective filtering surface, so that filter apparatuses of this type can be used commercially without difficulty. The utilization efficiency of the aroma carriers in such filter apparatuses is very good, regardless of whether the individual brewing charges are small or large, since even with small brewing charges the aroma carrier is very well centered in the region of the pyramid apex.
The water intake for such filter apparatuses may have a very simple configuration. For example, it may simply be the outlet opening of a corresponding overflow pipe, so that the water intake of such filter apparatuses is extremely resistant to calcium deposits and soiling.
Since the filter vessels of such filter apparatuses are generally equipped with ribs on which the filter paper inserts are supported, the generation of a subatmospheric pressure between a filter paper insert and the walls of the filter vessel may produce a certain suction effect which accelerates the filtration process.
Therefore, such filter apparatuses devices are also called quick filters.
The filter paper inserts themselves may be packaged in a flat state. Consequently no problems arise in connection with their stability in form and the ease of manipulation of the filter paper inserts.
However, it has also been found that, particularly in connection with large brewing charges, the aroma carrier cannot be utilized with optimum efficiency in the corner regions of the prior art filter apparatuses.